| In this paper we address the following probabilistic version (PSC) of the set covering
problem: $ min{cx | P(Ax ≥ ξ) ≥ p, x_j \in {0, 1} j \in N }$ where A is a 0-1 matrix, ξ
is a random 0-1 vector and $p \in (0, 1]$ is the threshold probability level. In a recent
development Saxena, Goyal and Lejeune proposed a MIP reformulation of (PSC) and
reported extensive computational results with small and medium sized (PSC) instances.
Their reformulation, however, suffers from the curse of exponentiality − the number of
constraints in their model can grow exponentially rendering the MIP reformulation intractable for all practical purposes. In this paper, we give a polynomial-time algorithm
to separate the (possibly exponential sized) constraint set of their MIP reformulation.
Our separation routine is independent of the specific nature (concave, convex, linear,
non-linear etc) of the distribution function of ξ, and can be easily embedded within a
branch-and-cut framework yielding a distribution-free algorithm to solve (PSC). The resulting algorithm can solve (PSC) instances of arbitrarily large block sizes by generating
only a small subset of constraints in the MIP reformulation and verifying the remaining
constraints implicitly. Furthermore, the constraints generated by the separation routine
are independent of the coefficient matrix A and cost-vector c thereby facilitating their
application in sensitivity analysis, re-optimization and warm-starting (PSC). We give
preliminary computational results to illustrate our findings on a test-bed of 40 (PSC)
instances created from OR-Lib set-covering instance scp41.
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